1.jpg-->png

- (void)jpgToPng{
    UIImage * image = [UIImage imageNamed:@"faust_github.jpg"];
    NSData * data = UIImagePNGRepresentation(image);
    UIImage * imagePng = [UIImage imageWithData:data];
    //图片保存到本地相册中
    UIImageWriteToSavedPhotosAlbum(imagePng, nil, nil, nil);
}

2.jpg-->jpg

- (void)jpgToJpg{
    UIImage * image = [UIImage imageNamed:@"faust_github.jpg"];
    NSData * data = UIImageJPEGRepresentation(image, 1);//1是质量因子，越小，图片越小
    UIImage * imagePng = [UIImage imageWithData:data];
    //图片保存到本地相册中
    UIImageWriteToSavedPhotosAlbum(imagePng, nil, nil, nil);
}

注：

• 1.imageNamed imageWithData
• 2.png无损，，jpg有损

3.播放gif图片

/**
 *  1.我们要拿到gif数据
 *  2.将gif分解一帧帧
 *  3.将单帧数据转为UIImage
 *  4.单帧图片保存
 */
- (void)viewDidLoad {
    [super viewDidLoad];
    [self deCompositionGif];
    [self ShowGIf];
}
/**
 *  展示gif
 */
- (void)ShowGIf{
    UIImageView * imageView = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 270, 115)];
    [self.view addSubview:imageView];
    [imageView setAnimationImages:gifArray];
    [imageView setAnimationRepeatCount:10];
    [imageView setAnimationDuration:1];
    [imageView startAnimating];
}
/**
 *  分解gif
 */
- (void)deCompositionGif{
    //1.我们要拿到gif数据
    NSString * gifPathSource = [[NSBundle mainBundle] pathForResource:@"paopao" ofType:@"gif"];
    NSData * data = [NSData dataWithContentsOfFile:gifPathSource];
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
    //2.将gif分解一帧帧
    size_t count = CGImageSourceGetCount(source);
    NSMutableArray * tmpArray = [NSMutableArray arrayWithCapacity:0];
    for (size_t i = 0; i < count; i++) {
        CGImageRef imageref = CGImageSourceCreateImageAtIndex(source, i, NULL);
        //3.将单帧数据转为UIImage
        UIImage * image = [UIImage imageWithCGImage:imageref scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
        [tmpArray addObject:image];
        CGImageRelease(imageref);
    }
    CFRelease(source);
    //4.单帧图片保存
    int i = 0;
    for (UIImage * img in tmpArray) {
        NSData * data = UIImagePNGRepresentation(img);
        NSArray * path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString * gifPath = path[0];
        NSLog(@"%@",gifPath);
        NSString * pathNum = [gifPath stringByAppendingString:[NSString stringWithFormat:@"%d.png",i]];
        i++;
        [data writeToFile:pathNum atomically:YES];
    }
    gifArray = [NSMutableArray arrayWithArray:tmpArray];
}

4.png--->gif

- (void)createGif{
    //1.获取我们的数据
    NSMutableArray * pngArray = [NSMutableArray arrayWithCapacity:0];
    for (int i = 1; i < 11; i++) {
        UIImage * image = [UIImage imageNamed:[NSString stringWithFormat:@"image%d.png",i]];
        [pngArray addObject:image];
    }
    //2.创建gif文件
    NSArray * document = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString * documentStr = [document objectAtIndex:0];
    NSFileManager * fileManager = [NSFileManager defaultManager];
    NSString * textDic = [documentStr stringByAppendingString:@"/gif"];
    [fileManager createDirectoryAtPath:textDic withIntermediateDirectories:YES attributes:nil error:nil];
    NSString * path = [textDic stringByAppendingString:@"test1.gif"];
    NSLog(@"%@",path);
    //3.配置gif属性
    CGImageDestinationRef destion;
    CFURLRef url = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)path, kCFURLPOSIXPathStyle, false);
    CGImageDestinationCreateWithURL(url, kUTTypeGIF, pngArray.count, NULL);
    NSDictionary * frameDic = [NSDictionary dictionaryWithObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithFloat:0.3], (NSString *)kCGImagePropertyGIFDelayTime, nil] forKey:(NSString *)kCGImagePropertyGIFDelayTime];
    NSMutableDictionary * gifParaDict = [NSMutableDictionary dictionaryWithCapacity:0];
    [gifParaDict setObject:[NSNumber numberWithBool:YES] forKey:(NSString *)kCGImagePropertyGIFHasGlobalColorMap];
    [gifParaDict setObject:(NSString *)kCGImagePropertyColorModelRGB forKey:(NSString *)kCGImagePropertyColorModel];
    [gifParaDict setObject:[NSNumber numberWithInt:8] forKey:(NSString *)kCGImagePropertyDepth];
    [gifParaDict setObject:[NSNumber numberWithInt:0] forKey:(NSString *)kCGImagePropertyGIFLoopCount];
    NSDictionary * gifProperty = [NSDictionary dictionaryWithObject:gifParaDict forKey:(NSString *)kCGImagePropertyGIFDictionary];
    //4.单帧添加到gif
    for (UIImage * image in pngArray) {
        CGImageDestinationAddImage(destion, image.CGImage, (__bridge CFDictionaryRef) frameDic);
    }
    CGImageDestinationSetProperties(destion, (__bridge CFDictionaryRef)gifProperty);
    CGImageDestinationFinalize(destion);
    CFRelease(destion);
    
}